The present invention is directed to ink jet printing processes on carbonless paper. More specifically, the present invention is directed to processes for selectively desensitizing areas of carbonless paper by the application of a desensitizing agent via an ink jet printing process. One embodiment of the present invention is directed to a printing process which comprises (a) incorporating into a printing apparatus capable of generating ink jet images a carbonless paper set comprising a first sheet, a second sheet, and optional intermediate sheets situated between the first sheet and second sheet, wherein the first sheet comprises paper coated on one surface with a color former and the second sheet comprises paper coated on one surface with a color developer, and wherein, when the carbonless paper set is assembled, the surface of the first sheet coated with the color former is in contact with the surface of a sheet coated with the color developer and the surface of the second sheet coated with the color developer is in contact with the surface of a sheet coated with the color former; (b) incorporating into the printing apparatus an ink jet ink comprising water, an organic component, and a desensitizing agent capable of interacting either (i) with the color former so that the color former's subsequent ability to interact with the color developer is reduced, or (ii) with the color developer so that the color developer's subsequent ability to interact with the color former is reduced; and (c) causing droplets of the ink containing the desensitizing agent to be ejected in an imagewise pattern onto either (i) at least one surface of one sheet coated with the color former, or (ii) at least one surface of one sheet coated with the color developer.
Carbonless paper sets generally are stacks of at least two sheets of paper wherein the application of pressure in imagewise fashion on the top sheet, typically by handwriting or typing, results in formation of a corresponding image on the underlying sheets, so that copies are formed as the image is generated on the top sheet. Carbonless paper sets typically comprise a top sheet of paper, on the bottom surface of which is coated a first composition, and a bottom sheet, on the top surface of which is coated a second composition. The first and second compositions are in contact with each other when the top and bottom sheets are placed in stack formation, and generally are of a nature such that application of pressure to the top sheet of the stack at a specified location causes interaction between the first and second compositions that results in the formation of a colored area on the bottom sheet at the location at which pressure was applied. Intermediate sheets can be located between the top and bottom sheets, wherein each intermediate sheet is coated on its top surface with the second composition and on its bottom surface with the first composition; application of pressure to the top sheet then results in the formation of a colored area at the location at which pressure was applied on each of the intermediate sheets and on the bottom sheet.
An example of a carbonless paper set is disclosed in U.S. Pat. No. 3,843,383, the disclosure of which is totally incorporated herein by reference. This patent discloses a recording sheet comprising a support having thereon a layer of color developer capable of reacting with a substantially colorless color former to form colored images. The paper set generally comprises a top sheet coated with microcapsules containing a color former solution, a bottom sheet coated with a color developer material in a binder, and, in some instances, middle sheets coated on one side with the color developer and on the other side with the color former microcapsules. Alternatively, the color former microcapsules and the color developer can be applied to the same surface of a paper. The color developer comprises a clay into which is incorporated at least one aromatic carboxylic acid or alkali metal salt thereof, and, optionally, acidic resins or inorganic pigments such as metal oxides, metal hydroxides, or metal carbonates. Suitable clays include acidic clay, active clay, attapulgite, zeolite, bentonite, kaolin, silicic acid, synthetic silicic acid, aluminum silicate, zinc silicate, colloidal silicic acid, and the like. The clay and the aromatic carboxylic acid or alkali metal salt thereof are formed into a coating solution which is then applied to paper. The color former is dissolved in a solvent and encapsulated in microcapsules, or is dissolved in a solvent and mixed with a binder. Contacting a sheet coated with microcapsules containing the color former under pressure with a sheet coated with the color developer results in formation of a color image. Other patents disclosing carbonless paper of this type include U.S. Pat. No. 2,712,507 and U.S. Pat. No. 2,730,456, the disclosures of which are totally incorporated herein by reference. Alternatively, as disclosed in U.S. Pat. No. 2,730,457, the disclosure of which is totally incorporated herein by reference, the color former microcapsules and the color developer of a carbonless paper can be applied to the same surface of a paper sheet. Other configurations of color former, color developer, and a pressure-releasable liquid solvent are possible, including, for example, those disclosed in U.S. Pat. No. 3,672,935, the disclosure of which is totally incorporated herein by reference. Additional patents disclosing carbonless papers and materials suitable for carbonless paper applications include U.S. Pat. No. 2,417,897, U.S. Pat. No. 3,672,935, U.S. Pat. No. 3,681,390, U.S. Pat. No. 4,202,820, U.S. Pat. No. 4,675,706, U.S. Pat. No. 3,481,759, U.S. Pat. No. 4,334,015, U.S. Pat. No. 4,372,582, U.S. Pat. No. 4,334,015, U.S. Pat. No. 2,800,457, U.S. Pat. No. 2,800,458, U.S. Pat. No. 3,418,250, U.S. Pat. No. 3,516,941, U.S. Pat. No. 4,630,079, U.S. Pat. No. 3,244,550, U.S. Pat. No. 3,672,935, U.S. Pat. No. 3,732,120, U.S. Pat. No. 3,843,383, U.S. Pat. No. 3,934,070, U.S. Pat. No. 3,481,759, U.S. Pat. No. 3,809,668, U.S. Pat. No. 4,877,767, U.S. Pat. No. 4,857,406, U.S. Pat. No. 4,853,364, U.S. Pat. No. 4,842,981, U.S. Pat. No. 4,842,976, U.S. Pat. No. 4,788,125, U.S. Pat. No. 4,772,532, and U.S. Pat. No. 4,710,570, the disclosures of each of which are totally incorporated herein by reference.
Frequently carbonless paper sets are printed as forms, wherein a large number of sets are printed with standard text or other material, leaving blank areas for individualized information to be filled in by, for example, impact typewriting or handwriting. Typically, carbonless pre-printed forms are generated by techniques such as offset printing. Offset printing and other large scale printing processes, however, require complex and expensive equipment which is not generally found in an office or small business environment. Thus, one desiring forms printed on carbonless paper generally must order them from a professional printer, thus generating added costs and inconvenience, particularly when only a relatively small number of the pre-printed forms are needed. The ability to generate pre-printed carbonless forms on standard office equipment thus can be desirable, particularly when small quantities of forms are desired.
In some instances, it may be desirable to desensitize selected areas of selected sheets of carbonless paper so that not all of the information written on a finished carbonless paper set (by, for example, handwriting or impact printing) appears on all of the carbonless copies. For example, in a multi-part invoice or receipt, some of the information recorded on some of the copies retained by the issuing company may be proprietary, and thus should not appear on the copies which are given to the customer. Previously, it has been possible to "block" or desensitize selected parts of forms printed by offset methods by printing those parts with a desensitizing ink during the offset printing of the carbonless sheets. This desensitizing offset ink reacts with the color developer to form a colorless product. When the carbonless paper set is subsequently subjected to handwriting or impact printing, microcapsules containing color former are broken in an imagewise pattern and the color former solution transfers to the color developer coating and reacts with the developer to form a colored image. In the desensitized areas, however, the color developer has already reacted with the desensitizing ink to form a colorless compound, and no color forming reaction can occur in these areas to form a carbonless image.
Known desensitizing processes, however, require the use of offset printing techniques. Thus, the desensitizing of selected areas of carbonless forms is not easily done in an office setting with common office or small business equipment. Accordingly, a process which would enable both printing and selective desensitization of carbonless papers in an office environment would be highly desirable.
Ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field which adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
Since drop-on-demand systems require no ink recovery, charging, or deflection, the system is much simpler than the continuous stream type. There are two types of drop-on-demand ink jet systems. One type of drop-on-demand system has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. The other type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets and allows very close spacing of nozzles. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink in the immediate vicinity to evaporate almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands. When the hydrodynamic motion of the ink stops, the process is ready to start all over again. With the introduction of a droplet ejection system based upon thermally generated bubbles, commonly referred to as the "bubble jet" system, the drop-on-demand ink jet printers provide simpler, lower cost devices than their continuous stream counterparts, and yet have substantially the same high speed printing capability.
The operating sequence of the bubble jet system begins with a current pulse through the resistive layer in the ink filled channel, the resistive layer being in close proximity to the orifice or nozzle for that channel. Heat is transferred from the resistor to the ink. The ink becomes superheated far above its normal boiling point, and for water based ink, finally reaches the critical temperature for bubble formation or nucleation of around 280.degree. C. Once nucleated, the bubble or water vapor thermally isolates the ink from the heater and no further heat can be applied to the ink. This bubble expands until all the heat stored in the ink in excess of the normal boiling point diffuses away or is used to convert liquid to vapor, which removes heat due to heat of vaporization. The expansion of the bubble forces a droplet of ink out of the nozzle, and once the excess heat is removed, the bubble collapses on the resistor. At this point, the resistor is no longer being heated because the current pulse has passed and, concurrently with the bubble collapse, the droplet is propelled at a high rate of speed in a direction towards a recording medium. The resistive layer encounters a severe cavitational force by the collapse of the bubble, which tends to erode it. Subsequently, the ink channel refills by capillary action. This entire bubble formation and collapse sequence occurs in about 10 microseconds. The channel can be refired after 100 to 500 microseconds minimum dwell time to enable the channel to be refilled and to enable the dynamic refilling factors to become somewhat dampened. Thermal ink jet processes are well known and are described in, for example, U.S. Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899, U.S. Pat. No. 4,412,224, and U.S. Pat. No. 4,532,530, the disclosures of each of which are totally incorporated herein by reference.
U.S. Pat. No. 2,777,780 (Cormack et al.), the disclosure of which is totally incorporated herein by reference, discloses a method of deactivating portions of record material sensitized with minute particles of inorganic adsorbent electron acceptor materials which cause the formation of color in an electron donor aromatic double bond color-reactant compound adsorbed thereon, by reason of an electron donor-acceptor color reaction which converts the compound to a more highly polarized conjugated form, giving it a distinctive color, including the step of applying to selected areas of the sensitized record material, before any of the organic color-reactant is applied, highly polar, non-volatile non-color-forming adsorbate material sufficient to occupy the normally available adsorbent sites on the particles of such areas. This reference discloses the desensitizing of electron acceptor color developer coatings with cationic quaternary ammonium salts, higher aliphatic or aryl amine acetates, high molecular weight primary amines and primary diamines such as dodecyl amine or dodecyl diamine, or substituted oxazolines.
U.S. Pat. No. 3,809,668 (Yarian) and U.S. Pat. No. 3,852,094 (Yarian), the disclosures of each of which are totally incorporated herein by reference, disclose desensitizing agents which, when combined with a suitable solvent, can be used to desensitize carbonless papers of the DTO/metal type wherein the DTO (Dithiooxamide) compound is encapsulated and is released for chemical interaction with a coreactant metal salt by rupture of the capsules. The preferred desensitizing agents are partial esters of ethylenediaminetetraacetic acid, which partial esters are soluble in suitable organic media and form stable, substantially colorless complexes with, for example, nickel salts. Various homologs and analogs of these partial ester derivatives are also operative in the invention, as are certain less preferred compounds, i.e., certain diamines, oximes, and vic.-dimercaptans. The preferred desensitizing agents are also useful for desensitizing carbonless papers of the leuco dye/acidic clay type.
U.S. Pat. No. 5,174,556 (Taylor et al.), the disclosure of which is totally incorporated herein by reference, discloses a document finisher which includes a printing station for printing on the binding of a book. The printing station in one embodiment prints on the binder tape before the book is bound. In a second embodiment, the printer prints on the binding after the book is bound. The printing stations are space efficient and designed to be easily incorporated with preexisting stations in document finishers. Ink jet printers and impact-type printer may be utilized.
U.S. Pat. No. 5,156,675 (Breton et al.), the disclosure of which is totally incorporated herein by reference, discloses fast drying ink compositions containing a colorant, a dye, water and a cosolvent. Some of the ink compositions dry in less than about 1 second and have a viscosity of between about 1.6 and about 2.5 centipoise and a specified surface tension. Some of the ink compositions contain specified cosolvents, preferably a mixture of diethylene glycol monobutyl ether and glycerol.
British Patent Application 2,030,932, the disclosure of which is totally incorporated herein by reference, discloses a copying paper having a color developing acidic material layer for developing color when contacted with a colorless dye which can be sufficiently desensitized on a portion which is not desired to be given an image by printing on the portion a desensitizing ink composition. The ink comprises a poly(oxypropylene)glycol or triol, a copolymer thereof with polyoxyethylene, an aliphatic alcohol or a phenol adduct thereof, or a carboxylic acid ester thereof, a pigment and a vehicle therefor according to dry lithography.
Japanese Patent Publication 91-71882, the disclosure of which is totally incorporated herein by reference, discloses a desensitizing agent for pressure-sensitive copying which is an aminostyrene polymer graft polymerized at the amino group by ethylene oxide, propylene oxide, or styrene oxide.
German Patent 2,727,194, the disclosure of which is totally incorporated herein by reference, discloses a desensitizer for carbonless copy paper which are hardenable by UV radiation.
U.S. Pat. No. 5,286,286 entitled "Colorless Fast-Drying Ink Compositions for Printing Concealed Images Detectable by Fluorescence," with the named inventors Francoise M. Winnik, Anthony R. Davidson, and Marcel P. Breton, the disclosure of which is totally incorporated herein by reference, discloses an ink composition consisting essentially of water, diethylene glycol-monobutyl ether, glycerol, an optional cyclohexyl pyrrolidinone component, a dye selected from the group consisting of dyes containing dansyl chromophores and dyes containing porphyrin chromophores, an optional biocide, and an optional polyalkylene oxide/bisphenol-A additive.
Copending application U.S. Ser. No. 07/616,971, filed Nov. 21, 1990, entitled "Carbonless Paper for Ink Jet Printing," with the named inventors John F. Oliver, Richard E. Sandborn, and David J. Sanders, now abandoned, the disclosure of which is totally incorporated herein by reference, discloses a process for generating images which comprises incorporating into an ink jet printing apparatus a carbonless paper set which comprises a first sheet comprising a support containing a color developer capable of reacting with a color former to produce a color image, said color developer comprising high surface area silica particles, and a second sheet comprising a support coated with the color former, forming an image on the first sheet by causing ink to be expelled in droplets on a surface containing the color developer, and forming an image on the second sheet by causing ink to be expelled in droplets onto the surface opposite to that coated with the color former.
U.S. Pat. No. 5,212,040, entitled "Carbonless Paper for Electrostatic Imaging Processes," with the named inventors David J. Sanders, John F. Oliver, and Marcel P. Breton, the disclosure of which is totally incorporated herein by reference, discloses a process which comprises incorporating into an electrostatic imaging apparatus a recording sheet comprising a support on one surface of which are situated microcapsules which comprise a shell and a core containing a color former and an oil, said microcapsules being strengthened with a polymer capable of degrading upon exposure to actinic radiation; generating an electrostatic latent image on an imaging member in the apparatus; developing the latent image with a developer; transferring the developed image to the recording sheet; and, subsequent to transfer, exposing the recording sheet to actinic radiation at a wavelength at which the polymer will degrade, thereby rendering the microcapsules subject to rupture upon application of pressure.
U.S. Pat. No. 5,223,475, entitled "Self-Cleaning Carbonless Paper," with the named inventors John F. Oliver and David J. Sanders, the disclosure of which is totally incorporated herein by reference, discloses a carbonless paper set having at least two sheets, wherein a first sheet comprises paper coated on one surface with a color former and a second sheet comprises paper coated on one surface with a color developer, and wherein at least one of the sheets contains an oleophilic pigment filler material on the surface of the sheet opposite to that coated with the color former or color developer. Also disclosed is a process for generating images which comprises generating an electrostatic latent image on an imaging member in an imaging apparatus, developing the latent image with toner particles of one polarity, contacting the developed image on the imaging member with the first sheet of the carbonless paper set disclosed herein, applying an electric charge of a polarity opposite to that of the toner particles to the surface of the first sheet opposite the surface in contact with the imaging member, thereby transferring the developed image to the first sheet, generating an electrostatic latent image on the imaging member in the imaging apparatus, developing the latent image with toner particles of one polarity, contacting the developed image on the imaging member with the second sheet of the carbonless paper set disclosed herein, applying an electric charge of a polarity opposite to that of the toner particles to the surface of the second sheet opposite the surface in contact with the imaging member, thereby transferring the developed image to the second sheet, and optionally permanently affixing the transferred images to the first and second sheets.
U.S. Pat. No. 5,373,350, entitled "Xerographic/Thermal Ink Jet Combined Printing," with the named inventors Thomas N. Taylor, LeRoy A. Baldwin, and Otto R. Dole, the disclosure of which is totally incorporated herein by reference, discloses a printer which combines the technologies of xerographic and thermal ink jet printing into a unit capable of high resolution text and color graphics. The printer is capable of forming a composite image, including a xerographic printing portion and a thermal ink jet (TIJ) printing portion, by printing the xerographic portion using known xerographic techniques and the thermal ink jet portion by a thermal ink jet printing array associated with the printer. The portions may be printed in any order, and may be dried by a drying station after printing of each portion or after both portions have been printed. At least one thermal ink jet printing array can serve as an annotator which is capable of printing additional information onto a copy, such as company letterhead, special instructions, addresses, or the like.
Accordingly, while known materials and processes are suitable for their intended purposes, a need remains for processes for desensitizing selected areas of selected carbonless paper sheets. In addition, a need remains for processes for desensitizing selected areas of selected carbonless paper sheets which can be carried out with equipment commonly found in office and small business environments. Further, there is a need for processes for both printing and selectively desensitizing carbonless paper sheets which can be carried out with equipment commonly found in office and small business environments. Additionally, a need exists for processes for rapidly printing and selectively desensitizing carbonless paper sheets by methods such as electrophotography, electrography, ionography, ink jet printing, or the like. There is also a need for processes for both printing and desensitizing carbonless paper sheets which can be carried out in an apparatus which enables printing of images via an electrophotographic, electrographic, ionographic, or ink jet processes and annotation of the images via an ink jet printing process.